A coordination polymer-derived Co3O4/Co–N@NMC composite material as a Zn–air battery cathode electrocatalyst and microwave absorber
Zn–air batteries, promising energy storage equipment with high energy density, light weight and a compact structure, are a perfect power source for electric vehicles. For a Zn–air battery, the activity of the air cathode electrocatalyst plays an important role in its performance. Here, employing a coordination polymer as a precursor, a composite material built from Co3O4 and Co–N active centres with nitrogen-doped mesoporous carbon as a matrix has been synthesized successfully. This composite material possesses outstanding activity and stability in the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) processes. It possesses a small half-wave potential (ORR1/2 = 0.786 V) and low overpotential (OER10 = 1.575 V) for the ORR and OER, respectively. With this composite material as an air cathode electrocatalyst, a rechargeable Zn–air battery was assembled successfully. During the discharge process, the maximum power density of this Zn–air battery is 122 mW cm−2 at 0.76 V. The specific capacity of this battery is 505 mA h g−1 at 25 mA cm−2. The voltage gap between the charge and discharge processes is only 0.744 V at 10 mA cm−2 and 1.308 V at 100 mA cm−2. This rechargeable battery also shows promising stability after long-term charge–discharge experiments. Furthermore, the composite material also exhibits outstanding microwave adsorption properties. Its maximum reflection loss (RL) arrives at −13.9 dB with a thickness of only 1.0 mm. Thus, we find that coordination polymers are an ideal precursor for Zn–air battery cathode electrocatalysts and microwave absorbers.